In Rainbows End, by Vernor Vinge, a 2006 science-fiction novel set in the near future, modern medicine brings a talented Chinese-American poet, Robert Gu, back from end-stage Alzheimer’s disease. Before treatment, Gu is bedridden and can neither talk nor remember his children. After the therapy, his memory returns, although he develops a different set of talents. Flowers for Algernon, the 1959 short story by Daniel Keyes, entertains a related fantasy in which a futuristic treatment transforms Charlie, a mentally retarded man, into a genius.

Though fanciful, both these works echo ­research hinting that certain chemical treatments can reinvigorate the ability to learn and remember even in the face of brain damage or innate mental deficits. The studies—so far done in mice and sea slugs—indicate that the key to such cognitive improvements lies in epigenetics, the study of changes in DNA that do not affect the genetic code. Instead these chemical changes influence gene expression—that is, how actively the gene is used to make protein. Such alterations, it turns out, can have a profound impact on long-term memory. A drug compound, or even an environmental manipulation, that acts as a kind of volume knob for gene expression could someday help treat memory disorders and facilitate learning.